High-frequency electrical apparatus



Feb. 7, 1950 R. B. NELSON 2,496,887

HIGH-FREQUENCY ELECTRICAL APPARATUS Filed June 25, 1945vll/l//l//ll/l/l/ Figbdl.

Inventor: Richard B. Ne\sor1,

y ap-,Z5 AttOTT-ley.

Patented Fel. 7, 1950 HGH-FREQUENCY ELECTRICAL APPARATUS Richard B.Nelson, Schenectady, N, Yr, assigner to General Electric Company, acorporation of` New York Application J une 23, 1945, Serial No. 601,123

(Cl. 25d-27.5) l

16 Claims.

My invention relates to high frequency electrical apparatus and moreparticularly to improved space resonant structures and tuning mechanismstherefor. While not limited thereto, my invention is particularlyadapted for tunable magnetron anode structures.

A variety of tunable magnetron constructions have been proposed in whichone or more tuning elements are moved with respect to the space resonantanode structure to vary the effective inductance and capacitance of theVarious circuits of the anode structure. An arrangement for varying boththe inductive and capacitive components of the resonant circuitincluding a pair of tuning disks arranged on opposite sides of theresonant anode structure is described and claimed in my applicationSerial No. 566,288, led December 2, 1944, now Patent No. 2,424,496,dated July 22, 1947, and assigned to the assignee of the presentinvention. In arrangements of this type the somewhat complicated tuningstructure introduces a number of additional resonant circuits which area source of considerable power loss. This structure is also diflicult tocool eiciently so that the power output of the device is limited. Inaccordance with the present invention, an improved resonant structure isprovided which is shaped so that both the inductive and capacitivereactance components may be controlled by a single tuning member.

It is an object of my invention to provide a new and improved spaceresonant str-ucture.

,It is another object of my invention to provide a new and improvedtunable space resonant structure.

It is still another object of my invention to provide a new and improvedtunable magnetron construction.

In accordance with the illustrated embodiment of my invention, I providean improved magnetron construction in which the space resonant anode maybe considered as a modification of the radial vane type in which each ofthe Vanes is partially cut away so that the cross section of the vane ina radial plane is essentially J-shaped. The longer arm of each of theJ-shaped vanes is secured to the wall of the enclosing envelope and theshorter arm extends a portion of the distance from the end of the vanetowards the wall of the envelope. A substantially planar tuning memberis received between the arms of the anode sections and is axiallymovable with respect to the structure by an improved supportingstructure including essentially an end wall of the envelope. This wallis sealed to the ductor.

side Wall of the envelope by a flexible bellows and is moved withrespect thereto by an adjusting collar which is threaded to an extensionof the envelope. The collar is rotatably carried by a hub extending fromthe movable end wall of the envelope. In the particular embodimentillustrated, the vanes are formed of copper tubing which is bent intothe desired form and mounted on the envelope wall with the ends thereofcommunicating with a header formed on the exterior of thetube wall andproviding passages for cooling uid. Certain features of this tubularanode vconstruction are described and claimed in my application SerialNo. 601,122 led concurrently herewith and assigned to the assignee ofthe present invention.

For a better. understanding of my invention, reference vmay be Vhad tothe following description taken in connection with the accompanyingdrawing and its scope will be pointed out in the appended claims. In thedrawing, Fig. 1 is an elevational view, in section, of a magnetrondevice embodying my invention, Fig. 2 is a sectional View taken alongthe line 2 2 of Fig. l, and Fig. 3 is a sectional view takenvalong theline 3-3 of Fig. 1.

Referring now to the drawing, the magnetron device embodying myinvention includes a gen erally cylindrical envelope I formed of copperor other good conducting material. Although the discharge device isillustrated in the drawing with the axis of the envelope horizontal, itis preferable that the device be mounted with the axis vertical and inthe folowing descriptionV the parts are referred to as if the tuningmechanism were at the upper end of the device. The envelope is closed atits lower end by a wall 2 preferably formed of fernico or sheet steeland having a marginal flange 3 which is adapted to be welded orotherwise bonded to a fernico or sheet steelextension 4 formed on thelower end of the cylindrical member Il. The end wall 2 is provided witha centrally located aperture surrounded by a depending circular ange 5to which a cathode mount 6 is sealed by means of a cylindrical insulator'I. The cathode mount 6 includes a circular header 8 to which is bondeda fernico sleeve 9. The other end of the sleeve 9 is sealed to the lowerend of the insulating cylinder 1. The cathode proper includes a pair ofhelical wires I0 and I I which are wound in bilar relation and joined attheir upper ends to the upper end of a conductor I2 which provides asupport and direct current cathode supply con- The conductor I2 isreceived in an opening formed in the center of a ferromagnetic member I3having a generally d-umbbell shape cross section, as shown in Fig. 3,and which is supported at its lower end by the header 8. End shields I4and I5 are also supported from the conductor I2. The free ends of thecathode elements ID' and II" are joined to-molybdenum inserts I6 andI'Ireceived;respectively, inthe ends of steel rods I8 and I9 which arereceived in the openings provided by the restricted portion of thedumbbell shaped member I3. Theserods are provided at the lower ends withfer'riico' sleeves and 2l, respectively, which are sealed by glass beads22 and 23 to fernico sleeves'ZIl and 25of larger diameter which are,inlturn, brazed to the header 8. The current supply connections with thesteel rods I8 and IS are provided by conductors 26 and 2'I which passthrough the sleeves 20 and 2I in spaced relation with respect theretoand are received in recesses formed in the lower ends off'thesteelrods.' With'tliis oonstr'uction'tle current supply circuits includethe'ferro'mag-netic members I3, I8and I3' which provide-"a portion of`the magnetic circuit-for providing'` a' magnetic field in theinterelectrode'- space. This: magnetic circuit also includes avcylindrical member 28 surrounding the members I3,' I8 and I9 andprojecting into the" interior ofthe discharge device and an annulardisk' 23 which is bra'zed/to the exterior of the' end wall- 2'.Apolefa'oef30 of theA magnet or electromagnet may be shaped to'v conformgenerally'with' the shape'ofthe disk 29 and to advantage may beslottedlat one'side to facili'- tate slipping it'- in plaoef around thesupporting' flange 5 and the insulator 'I. The Vconstruction justdescribed provides a very effective wayof' supporting and supplying;current to the cathode while at the Sametime'providingvr a magneticcircuit for distributing'the flux-in the desired-'relation with respectto thecathode;

The anode structure ofthe devicf'includesa plurality of space resonantcircuits defined' by anode sections, each of which is?A of" generallyJV-shaped *crossy section;

length of tubular conductor, such as'cppertubwhich is foldedl bacl;i on'itself tof provide radially extending# armv portions -32 and' 331 which?are received inopeningsiformed-mltlie wall ofY the' envelope I. TliLVtubingi isY shaped tov define' axially extending portions 34j andl 35joined'- toY the outer ends'of thef'a'rm portions 3,2-'adl33a'tl one endand joined' to'a-'looppqrti'o'n 36p? at' the' other end.- Aigener'ally'trapezoidalishaped-member 3l is'brazed to thelowe`edgeoffea`ch"loo'pe'dl conductor 35 and together4 therewith-form the`short arm of the .I-shapedY anode'seotion The extended armof themember-'31 cooperating' with atuning member 42" provides"Y for aneieetive` variation of the capacitance of'ftlie various space'-vresonant circuitsv withthe positionof the tuning' member. The ends of'the armportions 32 and-33 received in the wall of theV envelope? I com'-municate, respectively, with 1".\as'sag'es'v 38 and-39 formed in acircular header39" which' surrounds the-envelope.v Thisheader maybeforrned'in any' suitable way and in thfef illustrated embodiment is acopper ring which has1 been?machined to provide the pass'ages38 and-*.39and!their-bra'zed'v to the exterior oftheenvelope". `F'Iu'idsupplyconnections and 4'I`V com'n'iunicateg` respectively; with passages 38and 39. In prior' constructions' it is common'practice to' connectcond'ucA'ti'vfely` all of the even numbered' sections at" their-inner#ends to provide one group of strapped sections' andA'skillustr'at'edfinv the? drawing; each anode section 3'I 'is-formed'from ato connect all of the odd numbered sections together to provide asecond group. In the arrangement illustrated these straps are providedby conducting rods which join alternate sections and pass through theopening provided by the looped portion 36 of the intermediate anodesection. This arrangement is' claimed' and more f'ullyy described in myabove referred toc'opending application Serial No. 601,122.

rlhe shape of the anode sections described above makes possible a novelarrangement of the tuning member and its associated mechanism whichforms an important aspect of my invention. Referring now to the drawing,a tuning member inthe form of an annular disk 42 is received between theloop portion 3B of the anode members 3l and the radial arm portionsincluding tubular conductors 32 and 33. This disk is arranged inparallel relation to and between the opposed surfaces provided by theradial arm portions 32 of the anode sections andthe members' 3lv whichare' secured to the loop portions oi" the anode sections. The tuningmember 4211s supported from a disk 43, preferably formed of copper,which may be considered an' end wall of' the tubular envelope I', bymeans of a continuous cylindrical conductor 44'. Withrths tuningstructure, which'is'essentially a hollow cylinder with' one'endapertured to'receive the axially extendingportions of the anodesections, the' number of resonant frequencies introduced is a minimumandthe power loss in the tuning mechanism is very small. The cylinder44" and end wall 43' are slightly smaller in diameter than the cylinder45' which extends substantially beyond the end wall G3 and is in effecta continuation of thev 46 which hermetically seals the tub'e envelopeVand permits the desired relative' movement between tlie anodestructure'and' the tuning structure including the tuning disk 42.prevent substantial leakage of electromagnetic' flux past' the tuningmember 472'and'the supporting cylinder 44 a cylindrical extension4'I`is'providedonthe inner wall of the envelope with the upper edgethereof ush with the'upper edge of the radial arm portions' of the anodesections.' This extension may bel formed integrally with the tubeenvelope I if desired. l

Movement' of the tuning structure is effected by a threaded bushing' 48'which is secured to the outer race 49 of a ball bearing 5D. The threadedportion of the bushing is received in an adaptor 5I which rests on ashoulder formed on the Lipper end of the extension d5' of the envelopeof the device. The inner race 52 of the bearing is clamped in fixedrelation" with respect to a hub 53? whichv is bonded tothe upper side ofthe end wallv 43. The' clamping' is eiected by a disk-like melnber'nwhich issecured tof the upper end'of the hub to clamp the'in'ner race 52of the bearing against a shoulder' formed on the hub 53; As? illustratedin the drawing, the hub is provided with axially extending passageswhich are joined at their lower ends'by a groove for the reception of aU-sh'a'p'ed tube 51 which is" placed in position in the hu'b'befo're' itis bonded to theend wall 43i The tube 5'I forms a passage forcirculating cooling fluid through the tuning structure to' extract heattherefrom generated by high frequency currents low reluctancepath' forthe axial magnetic flux- In order to' are omitted during the exhaust and'for this' reason the central opening 59 in the hub 53 is threaded topermit it to be retained in position with respect to the tube envelopebyv a suitable jig (not shown).

l, High frequency electrical energy may be extracted from the device bya Vsuitable output circuit coupled with the space resonant structure. Inthe illustrated embodiment this output is of thel concentric type andincludes an inner conductor 6D having a looped portion 6l bolted orotherwise secured to one of the anode sections as shown at 62. The outerconductor 63 of the output line is joined to the tube envelope andterminates in a radially extending flange '64. A cylindrical sleeve 65is joined at one end to the flange 64 and sealed at the other end to abody of glass 66 which is, in turn, sealed to a conductor 61 which formsan extension of conductor 60. The conductor 61, as illustrated, islarger than the conductor 60 and is hollow to receive a iuid supplyconduit 68. The collar 65 is electrically connected with an outerconductor -69 of the `output transmission line by an adaptor 10. Asillustrated, the outer end of the conduit 61 is slotted in the regionbeyond the glass seal 66 to provide passages 1l for the cooling fluidintroduced by the conduit 68. This fluid is allowed to escape throughsimilar passages 1l formed at the end of conductor 69 adjacent theadaptor 10. Air or other cooling fluid is introduced to the conduit 68through a fitting 12, a section ofinsulating conduit 13 and a passage 14formed in a conductor 15 which forms an extension of conductor 61 andprovides the central conductor of the output transmission line.

Evacuation of the envelope is accomplished through an opening 16 formedin the wall of the device and surrounded by an outwardly extendingsleeve 11 which is closed by a header 18 and an exhaust tube 19. Theheader 18 also provides a support for a getter 80 having one endconnected with the header through a conductor 8| and the other endsealed to the header by means of a conductor 82 sealed to a collar 83 bya body of glass 84. The conductor 8l also provides a support for ashield 85 which prevents the getter material from depositing on theinterior of the envelope.

Although the features and advantages which characterize my invention arebelieved to be readily understood from the foregoing detaileddescription of the illustrated embodiment, a brief description of theoperation of the device may further emphasize them. As is wellunderstood, electrons emitted by the cathode elements I and I I move inthe interelectrode space under the resultant action of an electric fieldproduced by voltage applied between the anode and cathode and an axialmagnetic eld produced in the interelectrode space by pole pieces 3D and58. The resultant motion of these electrons is effective to excite theanode structure into os-cillation at a high frequency dependent in partupon the geometry of the anode and in part by the position of the tuningstructure including the tuning di'sll:` 42. With the disk in theintermediate position shown, the magnetron will operate at anintermediate' frequency. As the tuning member is moved downwardlytoward'the radial arm portions of the anode members, the electromagneticflux linking the various circuits dened by the anode sections isgradually cutoff, thereby decreasing the inductance of the anodemembers. At the same time the distance between the disk 42 Vand Athemembers 31 which form extensions of theoverhanging portions of the anodesections is increased, thereby decreasing the capacitance between theanodes and the disk 42', which latter has very little high-frequencyvoltage. Since the resonant'frequency of the anode structure isdetermined by the product of the inductance and capacitance'ofl theresonant elements, a downward motion of disk 42, by decreasing bothinductance and capacitance, causes a large increase in the operatingfrequency. Conversely, as the disk is moved upwardly the capacitance isincreased and the inductance is increased, with the result that theoperating frequency is decreased.

Magnetron devices embodying the present invention may be tuned over awide range and op` erated at high power. The tuning range is largepartially because of the relatively smaller distributed -capacity of theJ-shaped anode sections as compared with the conventional vane typesections and because of the effectiveness of the single tuning disk as atuning element for both the inductive and capacitive reactancecomponents. The tuning structure is essentially a hollow cylinderyhaving continuous walls except for the apertured end which receives aportion of the resonant anode, and for this reason has very few resonantfrequencies associated with. it whichl tend to absorb power and lowerthe tube elfi-` ciency as well as to generate unwanted heat. The tuningstructure is also well suited for cooling because of the relativelylarge heat conducting paths which are connected with the tube en velopeand which may be fluid cooled, as illus trated in the drawing. Theincorporation in the magnetic circuit of a part of the support for thetuning structure and of a portion of the supportv and lead-in for thecathode also improves the distribution of the flux in the interelectrodespace. It is believed apparentlthat the combination of these featuresproduces a high frequency device of high eciency-,relatively large poweroutput, and wide tuning range.

While I have shown and described a particular embodiment of myinvention. it will be obvious to those skilled in the art that changesand modicationsQmay-'be made without departing from my invention-Ain itsbroader aspects. and I. therefore, aim in the appended claims to coverall such changes and modifications as fall within the true spirit andscope of my invention.

What l claim as new and desire to secure by Letters Patentof the UnitedStates is:

- 1. A high frequency device comprising a sub stantially planar tuningmember, a space reso-l nant structure including a plurality of sectionsmounted in spaced relation to denne a plurality of coupled spaceresonant circuits, each of said sections having a substantially J-shapedcross section vin a plane perpendicular tosaid tuning memberwith thearms of said J extending subn stantially parallel to and on oppositesides of said tuning member, and means connected with said tuning memberfor moving said tuning to each other and with respect to the rstmentioned ferromagnetic member.

14. An electric discharge device of the magnetron type including anenvelope, a tuning member, a space resonant anode structure mounted insaid envelope and including a plurality of anode sections, the walls ofsaid anode sections dening coupled. space resonant circuits havingphysically displaced portions contributing respectively thepredominately capacitive and predominately inductive components of theresonant circuits, said portions being positioned oppositely withrespect to said tuning member so that said member may be moved towardone of said portions of each of said anode sections as it moves awayfrom the other of said portions, and means for moving said member.

15. A tunable magnetron device comprising a resonant electrode structureincluding a generally cylindrical array of radially extendingcircumferentially spaced anode sections defining a plurality of coupledspace resonant circuits, said anode structure including acircumferentially extending recess, an annular tuning member positionedin said recess and means joined to said tuning member and extendinggenerally in an axial direction with respect to said anode for movingsaid tuning member axially with respect to said anode so that saidtuning member moves away from one surface of said recess as it movestoward the opposed surface of said recess.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date Dallenbach July 25, 1939 Dow July 16,1946 Spencer Sept. 24, 1946 Hagstrum Apr. 8, 1947 De Walt July 29, 1947FOREIGN PATENTS Country Date Switzerland May 1, 1940 Switzerland 1 Oct.1, 1941 Number Number Disclaimer 2,496,887.Rz`chard B. Nelson,Schenectady, N. Y. HIGH-FREQUENCY ELECTRICAL APPARATUS. Patent datedFeb. 7, 1950. Disclaimer filed Aug. l0, 1950, by the assignee, GeneralElectric Company. Hereby enters this disclaimer of claims 9, l0, and l1of Said patent.

[Ocz'al Gazette September 1.9, 1950.]

